A logical network or “overlay network” is a communication network constructed on another underlying network, for example a physical network. The nodes of the logical network are linked by logical connections. Each of these connections corresponds to a path consisting potentially of several physical connections linking the machines of the underlying physical network. A logical network is constructed with the aid of a specific application or software. For example in a logical network of peer-to-peer type, the network is constructed on the basis of the peer-to-peer application executed on each of the nodes of said network.
A peer-to-peer network possesses a dynamics in that nodes enter and nodes exit this network regularly. Determining the dynamics of a peer-to-peer network then consists in determining the number of nodes entering the network and/or the number of nodes exiting this network, in the course of a predetermined period.
Determining the dynamics is beneficial to an operator for performing operations for monitoring a peer-to-peer network which the operator trusts for managing certain services, for example a data storage service. Determination of the dynamics of this network allows the operator to adapt the working of the nodes of said network. This makes it possible to maintain the service quality that must be ensured by the operator via the peer-to-peer network.
The determination of the dynamics of a network of peer-to-peer type is currently based on obtaining information that is centralized at the level of a server. This server dispatches messages, for example a connection request, to the nodes of the network that it ascertains as executing the peer-to-peer application. If the connection request fails, the server then obtains the item of information that the node has left the peer-to-peer network. This item of information is thereafter processed by the server so as to determine the number of nodes that have left the network in the course of the message dispatch period.
Although this procedure makes it possible to determine whether a node is still present at a given instant, it does not guarantee this presence throughout the message dispatch period. Dispatching the connection requests to the whole set of nodes of the network takes time. This is all the more true if the network comprises a large number of nodes. Thus a node which has responded favourably to the connection request at the start of the message dispatch period, is no longer necessarily present in this network at the end of this period. The determination of the number of nodes having left the network in the course of this dispatch period will therefore be erroneous.
To reduce this message dispatch period, it is possible to limit the number of nodes to be invoked and to extrapolate the results to the peer-to-peer network as a whole. However, the group of nodes chosen to be invoked by the server does not necessarily represent the dynamics of the peer-to-peer network as a whole.